Tolerability and safety of alosetron during long-term administration in female and male irritable bowel syndrome patients

Current and emerging drug options in the treatment of diarrhea predominant irritable bowel syndrome

INTRODUCTION

Irritable bowel syndrome diarrhea predominant (IBS-D) is a highly prevalent GI disease, affecting nearly a third of all patients diagnosed with irritable bowel syndrome. Current treatment options are limited.

AREAS COVERED

This review discusses the pharmacotherapeutic options for IBS-D including currently used medications, the two newly FDA approved medications, as well as emerging therapies with potential benefit in IBS-D. Particular emphasis is placed on rifaximin and eluxadoline and their possible use in IBS-D.

EXPERT OPINION

Current pharmacological treatment of IBS-D includes loperamide, bile acid sequestrants, antispasmodics, tricyclic antidepressants, alosetron, eluxadoline and rifaximin. The latter two treatments have significantly added to the pharmacotherapeutic options for patients suffering from IBS-D.

Targeted therapies for diarrhea-predominant irritable bowel syndrome

Irritable bowel syndrome (IBS) causes gastrointestinal symptoms such as abdominal pain, bloating, and bowel pattern abnormalities, which compromise patients’ daily functioning. Common therapies address one or two IBS symptoms, while others offer wider symptom control, presumably by targeting pathophysiologic mechanisms of IBS. The aim of this targeted literature review was to capture clinical trial reports of agents receiving the highest recommendation (Grade 1) for treatment of IBS from the 2009 American College of Gastroenterology IBS Task Force, with an emphasis on diarrhea-predominant IBS. Literature searches in PubMed captured articles detailing randomized placebo-controlled trials in IBS/diarrhea-predominant IBS for agents receiving Grade I (strong) 2009 American College of Gastroenterology IBS Task Force recommendations: tricyclic antidepressants, nonabsorbable antibiotics, and the 5-HT₃ receptor antagonist alosetron. Studies specific for constipation-predominant IBS were excluded. Tricyclic antidepressants appear to improve global IBS symptoms but have variable effects on abdominal pain and uncertain tolerability; effects on stool consistency, frequency, and urgency were not adequately assessed. Nonabsorbable antibiotics show positive effects on global symptoms, abdominal pain, bloating, and stool consistency but may be most efficacious in patients with altered intestinal microbiota. Alosetron improves global symptoms and abdominal pain and normalizes bowel irregularities, including stool frequency, consistency, and fecal urgency. Both the nonabsorbable antibiotic rifaximin and the 5-HT₃ receptor antagonist alosetron improve quality of life. Targeted therapies provide more complete relief of IBS symptoms than conventional agents. Familiarization with the quantity and quality of evidence of effectiveness can facilitate more individualized treatment plans for patients with this heterogeneous disorder.

Targeted therapies for diarrhea-predominant irritable bowel syndrome

Irritable bowel syndrome (IBS) causes gastrointestinal symptoms such as abdominal pain, bloating, and bowel pattern abnormalities, which compromise patients' daily functioning. Common therapies address one or two IBS symptoms, while others offer wider symptom control, presumably by targeting pathophysiologic mechanisms of IBS. The aim of this targeted literature review was to capture clinical trial reports of agents receiving the highest recommendation (Grade 1) for treatment of IBS from the 2009 American College of Gastroenterology IBS Task Force, with an emphasis on diarrhea-predominant IBS. Literature searches in PubMed captured articles detailing randomized placebo-controlled trials in IBS/diarrhea-predominant IBS for agents receiving Grade I (strong) 2009 American College of Gastroenterology IBS Task Force recommendations: tricyclic antidepressants, nonabsorbable antibiotics, and the 5-HT(3) receptor antagonist alosetron. Studies specific for constipation-predominant IBS were excluded. Tricyclic antidepressants appear to improve global IBS symptoms but have variable effects on abdominal pain and uncertain tolerability; effects on stool consistency, frequency, and urgency were not adequately assessed. Nonabsorbable antibiotics show positive effects on global symptoms, abdominal pain, bloating, and stool consistency but may be most efficacious in patients with altered intestinal microbiota. Alosetron improves global symptoms and abdominal pain and normalizes bowel irregularities, including stool frequency, consistency, and fecal urgency. Both the nonabsorbable antibiotic rifaximin and the 5-HT(3) receptor antagonist alosetron improve quality of life. Targeted therapies provide more complete relief of IBS symptoms than conventional agents. Familiarization with the quantity and quality of evidence of effectiveness can facilitate more individualized treatment plans for patients with this heterogeneous disorder.

Serotonin receptor modulators in the treatment of irritable bowel syndrome

The aim of this article is to review the pathophysiology and clinical role of serotonin receptor modulators used in the treatment of irritable bowel syndrome. Serotonin is an important monoamine neurotransmitter that plays a key role in the initiation of peristaltic and secretory refl exes, and in modulation of visceral sensations. Several serotonin receptor subtypes have been characterized, of which 5HT3, 5HT4, and 5HT1b are the most important for GI function. 5HT4 agonists (eg, tegaserod) potentiate peristalsis initiated by 5HT1 receptor stimulation. 5HT4 agonists are therefore useful in constipation predominant form of IBS and in chronic constipation. 5HT3 antagonists (Alosetron and Cilansetron) prevent the activation of 5HT3 receptors on extrinsic afferent neurons and can decrease the visceral pain associated with IBS. These agents also retard small intestinal and colonic transit, and are therefore useful in diarrhea-predominant IBS. Tegaserod has been demonstrated in several randomized, placebo controlled trials to relieve global IBS symptoms as well as individual symptoms of abdominal discomfort, number of bowel movements and stool consistency. Several randomized, controlled trials have shown that alosetron relieves pain, improves bowel function, and provides global symptom improvement in women with diarrhea-predominant irritable bowel syndrome. However, ischemic colitis and severe complications of constipation have been major concerns leading to voluntary withdrawal of Alosetron from the market followed by remarketing with a comprehensive risk management program.

Questioning the bacterial overgrowth hypothesis of irritable bowel syndrome: an epidemiologic and evolutionary perspective

Although studies indicate that small intestinal bacterial overgrowth (SIBO) is prevalent in irritable bowel syndrome (IBS), it remains unclear whether SIBO causes IBS. This review presents an epidemiologic and evolutionary inquiry that questions the bacterial overgrowth hypothesis of IBS, as follows. (1) Although the hypothesis may be biologically plausible, there is also a strong rationale for competing hypotheses; it is unlikely that SIBO is the predominant cause of IBS in all comers, because competing explanations are sensible and defensible. Moreover, data indicate that the test used to promulgate the SIBO hypothesis - the lactulose hydrogen breath test - may not have measured SIBO in the first place. (2) We do not have evidence of SIBO being absent before IBS symptoms, and present after IBS emerges. (3) There is not a dose-response relationship between small intestinal microbiota and IBS symptoms. (4) The relationship between SIBO and IBS is highly inconsistent among studies. (5) Many effective IBS therapies do not address SIBO at all, yet have a more favorable "number needed to treat" than antibiotics. (6) IBS does not behave like a traditional infectious disease, suggesting that microbes may not principally cause the syndrome. (7) Other factors may confound the relationship between SIBO and IBS, including proton pump inhibitors. (8) Whereas the brain-gut hypothesis is evolutionary sensible, the bacterial hypothesis is harder to defend from an evolutionary perspective. The article concludes that bacteria may contribute to some IBS symptoms, but that bacteria cannot be the only explanation, and a causal link between SIBO and IBS is not secure.

Quantifying women's stated benefit-risk trade-off preferences for IBS treatment outcomes

BACKGROUND

The Food and Drug Administration, currently, is exploring quantitative benefit-risk methods to support regulatory decision-making. A scientifically valid method for assessing patients' benefit-risk trade-off preferences is needed to compare risks and benefits in a common metric.

OBJECTIVES

The study aims to quantify the maximum acceptable risk (MAR) of treatment-related adverse events (AEs) that women with diarrhea-predominant irritable bowel syndrome (IBS) are willing to accept in exchange for symptom relief.

RESEARCH DESIGN

A stated-choice survey was used to elicit trade-off preferences among constructed treatment profiles, each defined by symptom severity and treatment-related AEs. Symptom attributes included frequency of abdominal pain and discomfort, frequency of diarrhea, and frequency of urgency. AE attributes included frequency of mild-to-moderate constipation and the risk of four possible serious AEs.

SUBJECTS

A Web-enabled survey was administered to 589 female US residents at least 18 years of age with a self-reported diagnosis of diarrhea-predominant IBS.

MEASURES

Preference weights and MAR were estimated using mixed-logit methods.

RESULTS

SUBJECTS were willing to accept higher risks of serious AEs in return for treatments offering better symptom control. For an improvement from the lowest to the highest of four benefit levels, subjects were willing to tolerate a 2.65% increase in impacted-bowel risk, but only a 1.34% increase in perforated-bowel risk.

CONCLUSIONS

Variation in MARs across AE types is consistent with the relative seriousness of the AEs. Stated-preference methods offer a scientifically valid approach to quantifying benefit-risk trade-off preferences that can be used to inform regulatory decision-making.

Using the incremental net benefit framework for quantitative benefit-risk analysis in regulatory decision-making--a case study of alosetron in irritable bowel syndrome

OBJECTIVE

There is consensus that a more transparent, explicit, and rigorous approach to benefit-risk evaluation is required. The objective of this study is to evaluate the incremental net benefit (INB) framework for undertaking quantitative benefit-risk assessment by performing a quantitative benefit-risk analysis of alosetron for the treatment of irritable bowel syndrome from the patients' perspective.

METHODS

A discrete event simulation model was developed to determine the INB of alosetron relative to placebo, calculated as "relative value-adjusted life-years (RVALYs)."

RESULTS

In the base case analysis, alosetron resulted in a mean INB of 34.1 RVALYs per 1000 patients treated relative to placebo over 52 weeks of treatment. Incorporating parameter uncertainty into the model, probabilistic sensitivity analysis revealed a mean INB of 30.4 (95% confidence interval 15.9-45.4) RVALYs per 1000 patients treated relative to placebo over 52 weeks of treatment. Overall, there was >99% chance that both the incremental benefit and incremental risk associated with alosetron are greater than placebo. As hypothesized, the INB of alosetron was greatest in patients with the worst quality of life experienced at baseline. The mean INB associated with alosetron in patients with mild, moderate, and severe symptoms at baseline was 17.97 (-0.55 to 36.23), 29.98 (17.05-43.37), and 35.98 (23.49-48.77) RVALYs per 1000 patients treated, respectively.

CONCLUSIONS

This study demonstrates the potential utility of applying the INB framework to real-life decision-making, and the ability to use simulation modeling incorporating outcomes data from different sources as a benefit-risk decision aid.

Alosetron for severe diarrhea-predominant irritable bowel syndrome: safety and efficacy in perspective

Irritable bowel syndrome affects 5-10% of North Americans, with an estimated one-third having a diarrhea-predominant form. Alosetron hydrochloride (Lotronex) is a serotonin receptor type 3 antagonist approved in early 2000 for use in women with diarrhea-predominant irritable bowel syndrome (IBS-D). Initial use was widespread, but infrequent serious adverse events of ischemic colitis and severe constipation-related complications prompted alosetron's voluntary withdrawal from the US market in November 2000. Unprecedented public request prompted its reintroduction in 2002 under a Risk Management Plan, including a more restricted indication and a Prescribing Program for Lotronex. Despite these measures, the use of alosetron has been very limited since its reintroduction. Possible deterrents to its use include concerns over safety and the possible medical-legal implications raised by the Risk Management Plan. It is also possible that changes in the natural history and/or diagnosis of IBS-D have reduced the target population. Given the unique regulatory history of alosetron, these issues continue to engender controversy. This article profiles these concerns and reviews the pharmacology, clinical efficacy and safety, and post-marketing experience with alosetron. Myths and misconceptions related to alosetron use, or lack thereof, are addressed to provide the reader with the evidence needed to make informed treatment decisions for their female patients with severe IBS-D.

Preclinical and early clinical investigations related to monoaminergic pain modulation

The balance between descending controls, both excitatory and inhibitory, can be altered in various pain states. There is good evidence for a prominent alpha(2)-adrenoceptor-mediated inhibitory system and 5-HT(3) (and likely also 5-HT(2)) serotonin receptor-mediated excitatory controls originating from brainstem and midbrain areas. The ability of cortical controls to influence spinal function allows for top-down processing through these monoamines. The links between pain and the comorbidities of sleep problems, anxiety, and depression may be due to the dual roles of noradrenaline and of 5-HT in these functions and also in pain. These controls appear, in the cases of peripheral neuropathy, spinal injury, and cancer-induced bone pain to be driven by altered peripheral and spinal neuronal processes; in opioid-induced hyperalgesia, however, the same changes occur without any pathophysiological peripheral process. Thus, in generalized pain states in which fatigue, mood changes, and diffuse pain occur, such as fibromyalgia and irritable bowel syndrome, one could suggest an abnormal engagement of descending facilitations with or without reduced inhibitions but with central origins. This would be an endogenous central malfunction of top-down processing, with the altered monoamine systems underlying the observed symptoms. A number of analgesic drugs can either interact with or have their actions modulated by these descending systems, reinforcing their importance in the establishment of pain but also in its control.

The language of medicine: words as servants and scoundrels

Progress in complex disorders requires clear thinking facilitated by clear language. Clinicians and scientists occasionally become captive to inaccurate language or meaningless terminology and this generates lazy thinking and impedes progress. Has this happened in the case of the functional gastrointestinal disorders (FGIDs), in general, and irritable bowel syndrome (IBS), in particular? FGIDs and, especially IBS, are common illnesses and an important burden on healthcare resources but, in general, have suffered from a lack of progress in the development of safe and effective treatment. Among FGIDs, IBS may be the best defined but significant lapses of accuracy in terminology persist. Among other FGIDs, the situation is more serious; imprecision and lack of consistency in terminology continue to mar progress. This article reviews the chequered history of terminology in this area and concludes that removing the obfuscation generated by poor usage of language should be the first step towards understanding the pathogenesis and improving the management of these, and similar, disorders.

Efficacy and tolerability of alosetron for the treatment of irritable bowel syndrome in women and men: a meta-analysis of eight randomized, placebo-controlled, 12-week trials

BACKGROUND

Stimulated 5-hydroxytryptamine-3 (5-HT(3)) receptors promote intestinal motility, secretion, and sensation, effects that are related to the known pathophysiology of irritable bowel syndrome (IBS). A previous meta-analysis of 6 randomized controlled trials of the 5-HT(3)-receptor antagonist alosetron found that this agent was associated with global improvement in symptoms, pain, and discomfort in patients with IBS.

OBJECTIVE

This was a meta-analysis of randomized, placebo-controlled trials that evaluated the efficacy and tolerability of alosetron for the management of IBS. It updated and expanded on the previous meta-analysis.

METHODS

PubMed, EMBASE, SCOPUS, Web of Science, and the cochrane central Register of controlled Trials were searched from 1966 through September 2007 for placebo-controlled trials that examined the efficacy and tolerability of alosetron in the management of IBS. The search terms were alosetron, 5-HT, irritable bowel, functional bowel diseases, and irritable colon. No language restriction was applied. The data were analyzed in terms of 2 main outcomes: global improvement in IBS symptoms and adequate relief of IBS pain and discomfort.

RESULTS

Eight multicenter, randomized, placebo-controlled, 12-week clinical trials met the criteria for inclusion in the meta-analysis. The studies included 4,170 patients with IBS (80% female) who were randomized to receive either alosetron or placebo. All patients met the Rome criteria for IBS, and all subtypes of IBS were represented. Most patients had diarrhea-predominant IBS; only 2.6% of patients had constipation-predominant IBS. In the 3 trials included in the analysis of global improvement in symptoms, alosetron was significantly more effective than placebo (relative risk [RR] = 1.60; 95% CI, 1.44-1.76; P <0.001). In the 6 trials included in the analysis of adequate relief of IBS pain and discomfort, there was also a significant difference in favor of alosetron (RR = 1.31; 95% CI, 1.20-1.43; P < 0.001). Analysis of adequate relief of IBS pain and discomfort by sex also indicated significant differences between alosetron and placebo in both sexes (female: RR = 1.34 [95% cI, 1.21-1.48]; male: RR = 1.23 [95% CI, 1.02-1.47]). The analysis of tolerability, which was based on data from 7 studies, found a significant difference between alosetron and placebo (RR = 1.19; 95% cI, 1.07-1.31; P<0.001). The only adverse events that occurred with a significantly higher incidence in those treated with alosetron compared with placebo were constipation in 8 trials (RR = 4.35; 95% CI, 3.01-6.26; P < 0.001) and abdominal pain and discomfort in 5 trials (RR = 1.96; 95% CI, 1.46-2.64; P < 0.001). In the alosetron group, there were 4 cases of ischemic colitis (0.16%) and 2 cases of serious complications of constipation (0.08%); neither of these was reported in the placebo group. Alosetron was not associated with any deaths.

CONCLUSIONS

Alosetron was effective in these men and women with IBS. constipation was the most frequently reported adverse event associated with alosetron therapy. Ischemic colitis and serious complications of constipation were reported in a small number of patients treated with alosetron.

Effects of 5-hydroxytryptamine (serotonin) type 3 antagonists on symptom relief and constipation in nonconstipated irritable bowel syndrome: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND & AIMS

We performed a systematic review and meta-analyses to estimate treatment efficacy and constipation rate of 5-hydroxytryptamine (serotonin) (5-HT(3)) antagonists in patients with nonconstipated (NC) or diarrhea-predominant (D)-irritable bowel syndrome (IBS).

METHODS

Two reviewers independently searched MEDLINE, EMBASE, and Web of Science (January 1, 1966 to December 15, 2006) for randomized controlled trials of 5-HT(3) antagonists in IBS reporting clinical end points of the IBS symptom complex and safety parameters. Study characteristics, markers of methodologic quality, and outcomes for the intention-to-treat population for each randomized controlled trial were extracted independently.

RESULTS

We found 14 eligible randomized controlled trials of alosetron (n = 3024) or cilansetron (n = 1116) versus placebo (n = 3043) or mebeverine (n = 304). Random-effects meta-analyses found 5-HT(3) antagonists more effective than the comparators in achieving global improvement in IBS symptoms (pooled relative risk, 1.60; 95% confidence interval [CI], 1.49-1.72; I(2) = 0%) and relief of abdominal pain and discomfort (pooled relative risk, 1.30; 95% CI, 1.22-1.39; I(2) = 22%). Benefit was apparent for both agents, in patients of either sex. These agents were more likely to cause constipation (pooled relative risk, 4.28; 95% CI, 3.28-5.60, I(2) = 65%); there was less constipation with 5-HT(3) antagonists in D-IBS patients than in mixed populations (NC-IBS and D-IBS; relative risk ratio, 0.65; 95% CI, 0.41-0.99). Nine patients (0.2%) using 5-HT(3) antagonists had possible ischemic colitis versus none in control groups.

CONCLUSIONS

5-HT(3) antagonists significantly improve symptoms of NC-IBS or D-IBS in men and women. There is an increased risk of constipation with 5-HT(3) antagonists, although the risk is lower in those with D-IBS.

Systematic review: the safety and tolerability of pharmacological agents for treatment of irritable bowel syndrome--a European perspective

AIM

To use an evidence-based approach to evaluate the safety and tolerability of the treatments available for irritable bowel syndrome (IBS), or in clinical development, in Europe. A separate review appraises the evidence for the efficacy of these therapies.

METHODS

A literature search (for 1980 to 2005) was completed for all relevant clinical trial data and other articles which included safety information on the use of pharmacological IBS therapies. Clinical trials were scored according to the level of safety information, and adverse event incidence reported when possible.

RESULTS

The tolerability of many of the agents used to treat IBS in Europe is poorly understood. However, serotonergic agents, such as tegaserod and alosetron, which are currently unavailable in Europe, have undergone rigorous assessment in IBS and their benefits have been established. Following initial marketing of alosetron for use in patients with IBS with diarrhoea, concerns about severe constipation and ischaemic colitis resulted in restriction of its use to women with severe IBS symptoms. This highlights the importance of post-marketing surveillance and post-marketing studies in refining the therapeutic indication of new IBS therapies, which will help to identify appropriate recipients for the drug and establish the impact of adverse reactions in clinical practice.

CONCLUSIONS

There is a significant lack of data on the safety and tolerability of the therapies currently used routinely to treat IBS in Europe. The newer agents have undergone rigorous assessment, such that their benefits and risks in treating IBS are established. Defining their place among the spectrum of available therapies remains challenging when the benefits and risks of the older treatments are so poorly characterized.

Cisplatin's tumoricidal effect on human breast carcinoma MCF-7 cells was not attenuated by American ginseng

PURPOSE

We previously observed that American ginseng berry and ginsenoside Re attenuated cisplatin-induced emesis in a rat model, suggesting that the herb may have a value in treating chemotherapy-induced nausea/vomiting. However, it is not clear whether consuming ginseng concurrently with chemotherapy affects the efficacy of chemotherapeutic agents. In this study, we explored if the ginseng extract and its constituents, ginsenosides Rb1, Rb3, and Re, alter tumoricidal activity of cisplatin in human cancer cells.

METHODS

Tumoricidal effects of cisplatin, and/or American ginseng berry extract (AGBE) and ginsenosides Rb1, Rb3, and Re, on human breast carcinoma MCF-7 cells were measured as cell proliferation in vitro. Cell counts were performed in MCF-7 cells pretreated with test agents for 72 h.

RESULTS

Cisplatin decreased MCF-7 cell proliferation significantly in a concentration-dependent manner. Compared to control group, cisplatin reduced the cell proliferations to 56.5+/-3.3% at 1 microg/ml, to 36.6+/-2.4% at 5 microg/ml, and to 26.9+/-2.4% at 15 microg/ml (P<0.01). AGBE also inhibited the cell proliferation significantly, although in a less extended manner. When the berry extract at 0.5 mg/ml was used with cisplatin at 1 microg/ml, a significant enhancement of cisplatin's activity was observed (35.8+/-2.5%; P<0.05). We also observed that Rb1 did not change cisplatin's activity; Rb3, at a higher concentration, increased cisplatin's anti-proliferation activity (48.0+/-1.2%; P<0.05); Re increased cisplatin's activity (Re 0.1 mg/ml, 48.0+/-2.8%; Re 0.3 mg/ml, 31.9+/-2.2%, P<0.01).

CONCLUSION

Our data suggest that AGBE and the tested ginsenosides do not attenuate cisplatin's tumoricidal activity in MCF-7 cells, but in fact may actually enhance it. Additionally, the ginseng extract and ginsenoside Re by themselves exerted anti-proliferative activity against MCF-7 cells. The herb might potentially serve a complementary role with the chemotherapeutic agents in treating cancer, in addition to decreasing chemotherapy-induced nausea/vomiting.

Polyphenol contents in grape-seed extracts correlate with antipica effects in cisplatin-treated rats

BACKGROUND

Grape-seed (Vitis spp.) extract (GSE) is a widely used antioxidant dietary supplement. Chemotherapeutic agents such as cisplatin induce oxidative damage in the gastrointestinal tract and cause nausea and vomiting.

MATERIALS AND METHODS

A rat model of simulated emesis was used to observe that cisplatin significantly increased kaolin consumption (or pica). Three GSEs from different sources were used in this study.

RESULTS

High-performance liquid chromatographic analysis of five major constituents (gallic acid, catechin, epicatechi, procyanidin B2, and epicatechin gallate) revealed that each constituent had different levels in the three GSEs. Extract #1, prepared in the laboratory of the investigators, had the lowest total polyphenol content (27.27 mg/g); Extract #2, obtained from a dietary supplement company in the United States, had a somewhat higher level (35.84 mg/g); and Extract #3, obtained from China, had the highest level (194.21 mg/g). Subsequently these GSEs were intraperitoneally administered in rats to evaluate their ability to decreasing cisplatin induced pica. At 10 mg/kg all three GSEs, with varying degrees of effect, decreased cisplatin-induced pica. The areas under the curves of kaolin intake from time 0 to 72 hours, compared to those in the cisplantin-only group, were reduced 45% for Extract #1 (p < 0.01), 54% for Extract #2 (p < 0.01), and 66% Extract #3 (p < 0.001).

CONCLUSIONS

The study data showed variable polyphenol contents and proportions in the three GSEs correlated to variable pharmacologic effects, indicating the importance of standardization of herbal product preparations. However further increasing of the GSE doses reversed the antipica effects of GSEs, probably because of their pro-oxidant effects. Results from this study suggest that an appropriate dose of GSE has therapeutic value in treating cisplatin-induced emesis.

Incidence of ischemic colitis and serious complications of constipation among patients using alosetron: systematic review of clinical trials and post-marketing surveillance data

BACKGROUND

Ischemic colitis and serious complications of constipation have been reported in association with the use of alosetron, which is approved for women with severe diarrhea-predominant IBS who have failed conventional therapies. This systematic review calculated the incidence of these adverse events in alosetron-using patients in clinical trials and post-marketing surveillance.

METHODS

A panel of experts in epidemiology and functional bowel disorders reviewed clinical trial report forms and FDA MedWatch forms of each reported case of ischemic colitis or serious complications of constipation. Experts were blinded about whether patients used alosetron or placebo. Using pre-specified criteria, experts rated the likelihood of an accurate diagnosis and an association between medication use and adverse events. Cases that were not consistent with the reported diagnosis or not possibly associated with medication use were eliminated from calculation of incidence rates of adverse events.

RESULTS

Pooled data from clinical trials indicate an increased rate of ischemic colitis among alosetron-using patients compared to placebo-using patients (0.15%vs 0.0%, respectively, p = 0.03), but there was no significant difference in the rate of serious complications of constipation. All (19/19) alosetron-using patients with ischemic colitis had reversible colitis without long-term sequelae. Based on post-marketing surveillance data, the post-adjudication rate of ischemic colitis is 1.1 per 1,000 patient-years of alosetron use and the rate of serious complications of constipation is 0.66 per 1,000 patient-years of alosetron use.

CONCLUSION

The incidence of ischemic colitis and serious complications of constipation is very low and is rarely associated with long-term sequelae or serious morbidity.

Characterization of the metabolites of alosetron in experimental animals and human

The metabolism of radiolabelled alosetron was studied in rat, dog, rabbit, mouse and human. The metabolism in rat and dog was studied at a low and an elevated dose designed to generate sufficient quantities of metabolite for definitive identification. A strategy for the characterization of metabolites in cases of extensive metabolism was developed and demonstrated for alosetron. Semi-preparative high-performance liquid chromatography (HPLC), liquid chromatography-mass spectrometry (LC-MS), nuclear magnetic resonance (NMR) and liquid chromatography-nuclear magnetic resonance (HPLC-NMR) enabled the isolation and characterization of 28 metabolites of alosetron. The characterization of the metabolites in animal excreta facilitated the identification of human systemic metabolites.

A dose-ranging, phase II study of the efficacy and safety of alosetron in men with diarrhea-predominant IBS

BACKGROUND

A randomized, double blind, placebo-controlled dose-ranging study was conducted to assess the efficacy of alosetron in men with diarrhea-predominant irritable bowel syndrome (IBS).

METHODS

Six hundred and sixty-two men were randomized to treatment with alosetron 0.5, 1.0, 2.0, 4.0 mg, or placebo twice daily for 12 wk, followed by a 4-wk posttreatment period. Adequate relief of IBS pain and discomfort during week 5-12 of the treatment phase was the primary endpoint; secondary endpoints included bowel urgency, stool frequency, and consistency, incomplete evacuation, bloating, and abdominal pain or discomfort.

RESULTS

Subjects ranked urgency and abdominal pain as their most bothersome IBS symptoms. The average rate of adequate relief during week 5-12 was significantly higher in the alosetron 1.0 mg twice-daily group compared to placebo (53%vs 40%, p= 0.04), and all doses of alosetron significantly reduced stool consistency scores (p < 0.001) indicating firmer stools. No significant effects of alosetron were seen with regard to urgency, number of bowel movements, bloating, and incomplete evacuation. Constipation was the most common adverse event and occurred in a dose-related manner among subjects receiving alosetron, 9% (0.5 mg twice daily), 15% (1.0 mg twice daily), 11% (2.0 mg twice daily), and 21% (4.0 mg twice daily). No serious adverse events of constipation were reported. One subject in the 0.5 mg twice-daily group had an episode of rectal bleeding suggestive of a possible diagnosis of ischemic colitis.

CONCLUSIONS

Alosetron 1 mg twice daily provided adequate relief of IBS pain and discomfort, and improved stool consistency in men with diarrhea-predominant IBS.

Long-term safety and efficacy of alosetron in women with severe diarrhea-predominant irritable bowel syndrome

OBJECTIVES

To assess long-term safety and efficacy of alosetron in women with severe, chronic diarrhea-predominant IBS and in a subset having more frequent urgency (i.e., bowel urgency at least 10 of 14 days during screening).

METHODS

Randomized patients received either alosetron 1 mg (n = 351) or placebo (n = 363) twice daily during a 48-wk, double-blind study. The primary endpoint was the 48-wk average rate of adequate relief of IBS pain and discomfort. Secondary endpoints included 48-wk average satisfactory control rates of urgency, stool frequency, stool consistency, and bloating. Other efficacy endpoints were average monthly adequate relief and urgency control rates and impact of provided rescue medication.

RESULTS

Alosetron-treated patients had significantly greater 48-wk average adequate relief (p= 0.01) and urgency control (p < 0.001) rates, regardless of rescue medication use, compared with placebo. Results in subjects with more frequent urgency were more robust than those in the overall population (p= 0.005). In weeks without rescue medication use, satisfactory control rates for stool frequency and stool consistency were significantly greater in alosetron-treated patients than placebo. Alosetron-treated patients had significantly greater adequate relief than placebo-treated patients (p < 0.05) in 9 of 12 months and significantly greater urgency control (p < 0.001) in all months. Adequate relief and urgency control were maintained throughout the treatment. Adverse events and serious adverse events were similar between treatment groups, except for constipation. Neither ischemic colitis nor serious events related to bowel motor dysfunction was reported.

CONCLUSIONS

Long-term use of alosetron is effective and well-tolerated in women with chronic, diarrhea-predominant IBS, including those with more frequent urgency.

Effect of alosetron on bowel urgency and global symptoms in women with severe, diarrhea-predominant irritable bowel syndrome: analysis of two controlled trials

BACKGROUND & AIMS

The aim of this study was to assess the effect of alosetron on bowel urgency and irritable bowel syndrome (IBS) global improvement in diarrhea-predominant IBS (D-IBS).

METHODS

Women with a lack of satisfactory bowel urgency control at least 50% of the time during screening were randomized to receive alosetron 1 mg (n = 246) or placebo (n = 246) twice daily. The primary end point was the percentage of days with satisfactory control of bowel urgency. The response rate for the IBS global improvement scale (GIS) was a secondary end point. GIS responders were patients who recorded either moderate or substantial improvement in IBS symptoms relative to the way they felt before entering the study. Other end points included improvement in stool frequency, stool consistency, and percentage of days with incomplete evacuation. Further analyses were performed on a subset of patients who had at least 10 of 14 days during screening (>/=71% of days) with a lack of satisfactory control of bowel urgency.

RESULTS

Patients had severe chronic IBS symptoms, and 89% of patients had D-IBS. Alosetron resulted in a greater percentage of days with satisfactory control of urgency compared with placebo (69% vs. 56%, respectively, P < 0.001). Greater percentages of alosetron-treated patients were GIS responders at 4, 8, and 12 weeks compared with placebo (59% vs. 41%, 63% vs. 41%, and 68% vs. 46%, respectively, P < 0.001). Patients with more frequent urgency had similar results. Constipation occurred in 28% and 9% of subjects in the alosetron- and placebo-treated groups, respectively. No cases of ischemic colitis were reported.

CONCLUSIONS

Alosetron effectively manages bowel urgency and improves global symptoms in women with severe chronic D-IBS.

Alosetron and irritable bowel syndrome

Alosetron (Lotronex, GlaxoSmithKline) is a potent and selective 5-HT(3)-receptor antagonist approved by the FDA for the treatment of women with diarrhoea-predominant irritable bowel syndrome (IBS) in whom conventional therapy has failed. Studies involving healthy volunteers and IBS patients have demonstrated a beneficial effect of treatment with alosetron on global IBS symptoms, abdominal pain and discomfort, altered bowel function as well as improvement of quality of life (QOL). Data from animals studies suggest the involvement of 5-HT(3) receptors on intrinsic primary afferent neurons in the mediation of the effect of alosetron on gastrointestinal motility and secretion. While definitive proof of a visceroanalgesic action is not available, an additional central mechanism of action is suggested by findings obtained in animal models, as well as from human brain imaging studies. Alosetron shows a greater effectiveness in women, and the role of genetic factors underlying inter-individual differences in the response to alosetron is currently under investigation. The most frequent adverse event associated with the use of alosetron is constipation and in some rare cases, the development of colonic mucosal ischaemia. In the following review, the most recent reported effects of alosetron on gastrointestinal motility, visceral sensitivity and anxiety, both in terms of preclinical and clinical data will be discussed. The impact of alosetron on QOL in IBS patients and the safety of treatment with alosetron, will also be covered.

A new look at irritable bowel syndrome [IBS]: a neuroenteric disorder

Irritable bowel syndrome is difficult to treat because of poorly defined pathophysiology, lack of diagnostic marker, and until recently, limited pharmacotherapy. After diagnosis, treatment includes diet and behavior modifications, along with pharmacologic treatment for mild disease and severe cases.

The irritable bowel syndrome

Symptoms of IBS are very prevalent. One quarter of symptomatic individuals present for medical care because of symptom severity and psychologic factors. The pathogenesis of IBS is multifactorial, involving abnormalities in the gut, immune system, enteric sensory and motor nerves, and the CNS. IBS is diagnosed by symptomatology according to the Rome criteria and the absence of alarm findings suggestive of organic disease. Minimal testing is advocated to confirm the diagnosis in patients presenting with typical symptoms. Therapy is based on the dominant symptom (IBS subtype). Therapeutic options include dietary modifications, counseling, medications, and psychologic treatments. Novel therapies are being investigated to correct potentially pathogenetic peripheral and CNS abnormalities in IBS.

Serotonin transporter gene polymorphism in irritable bowel syndrome

OBJECTIVES

Serotonin is a key mediator of intestinal peristalsis, and after it is secreted, it is effectively cleansed from the neuronal gap by means of a high affinity substance called serotonin transporter (SERT), which depends on the Na+ and Cl- ions localized in the presynaptic neuronal membranes. The aim of this study was to investigate SERT polymorphism in patients with irritable bowel syndrome (IBS).

METHODS

SERT gene polymorphism was assessed by polymerase chain reaction on DNA chains obtained from leukocytes in serum samples from 54 patients diagnosed with IBS and 91 healthy subjects. The polymorphism of two regions (variable number tandem repeats and the SERT gene-linked polymorphic region [5-HTTLPR]) of SERT was assessed.

RESULTS

SERT polymorphisms were found to be similar in healthy subjects and IBS patients (p > 0.05). IBS patients were divided into three groups: diarrhea predominant (n = 18), constipation predominant (n = 26), and alternating diarrhea and constipation (n = 10). These groups were compared with respect to gene polymorphism, and it was found that the 5-HTTLPR allele S/S genotype occurred with greater frequency in the constipation predominant group than in the other two subgroups (p < 0.05), and L/S genotype frequency in the diarrhea predominant group was higher than those in the constipation and control groups.

CONCLUSIONS

No relationship was found between IBS and SERT gene polymorphism. It is conceivable that the presence of the S/S genotype in IBS patients carries an increased risk of the constipation predominant type of IBS, whereas the presence of the 5-HTTLPR allele L/S genotype carries an increased risk of the diarrhea predominant type.

Alosetron controls bowel urgency and provides global symptom improvement in women with diarrhea-predominant irritable bowel syndrome

OBJECTIVES

Bowel urgency is one of the most bothersome symptoms for nonconstipated IBS patients. The efficacy of alosetron in control of bowel urgency and Global Improvement of IBS symptoms were evaluated in a multicenter double-blind, randomized, placebo-controlled study.

METHODS

Female IBS patients with lack of satisfactory control of bowel urgency were randomized 2:1 to alosetron 1 mg twice daily or placebo treatment groups. The primary endpoint was the proportion of days with satisfactory control of bowel urgency during the 12-wk treatment period and 2-wk follow-up period. Secondary endpoints included IBS Global Improvement (responder defined as patient-reported moderate or substantial improvement in IBS symptoms) and improvements in bowel function (stool frequency, consistency, and sensation of incomplete evacuation).

RESULTS

A total of 801 women were randomized to the alosetron (n = 532) or placebo groups (n = 269). Physicians classified 98% of patients with diarrhea-predominant IBS. Patients treated with alosetron had a significantly greater proportion of days with satisfactory control of urgency compared to placebo for the treatment period (73% vs 57%, p < 0.001). A significantly greater number of patients treated with alosetron were IBS Global Improvement responders compared to placebo at week 12 (76% vs 44%, p < 0.001). IBS Global Improvement responders had more days with satisfactory control of urgency at week 12 (88% vs 48%) as well as firmer stools, fewer stools/day, and fewer days with incomplete evacuation compared with nonresponders. Alosetron-treated patients showed improvements in bowel functions compared to placebo-treated patients. Constipation was the most commonly reported adverse event.

Postinfectious Irritable Bowel Syndrome

Postinfectious irritable bowel syndrome (PI-IBS) should be considered in patients who present with a change in bowel habits or an onset of new abdominal pain or discomfort following a recent confirmed or presumed exposure to infectious organisms, or in those who have recently returned from a tropical or developing country. In patients who are greatly distressed by their symptoms, an extended workup early in the course of their illness may give physician and patient confidence in focusing on IBS. The author favors a proactive, multicomponent approach to management, as it gives the physician and patient a sense of control. Treatment should include stress management, dietary advice to minimize exposure to trigger foods, and pharmacotherapy to alleviate anxiety and target disturbed physiology.